1. Field of the Invention
The present invention relates to a linear actuator for effecting reciprocating motion of a slider in an axial direction of an actuator body by introducing a pressure fluid from either of fluid inlet/outlet ports.
2. Description of the Related Art
A conventional linear actuator has been used as a means for transporting a workpiece or the like.
For example, Japanese Utility Model Registration Publication No. 2607486 discloses a linear actuator concerning a conventional technique. As shown in FIG. 13, the linear actuator 1 comprises a pair of cylinder chambers 3a, 3b which are formed in a main cylinder body 2. A long hole 4, which is communicated with the cylinder chambers 3a, 3b, is formed to penetrate from the upper surface of the main cylinder body 2 to the lower surface of the main cylinder body 2 so that the long hole 4 is perpendicular to the axis of the main cylinder body 2. A pair of pistons 5a, 5b is independent from each other. Each of the pistons 5a, 5b is slidably inserted into the cylinder chambers 3a, 3b respectively. A rod 6, which is inserted in the vertical direction from a lower portion of the main cylinder body 2, is interposed between the pair of pistons 5a, 5b. 
The rod 6 is integrally connected to a table 7 which is arranged displaceably in the axial direction on the upper surface of the main cylinder body 2. Each of end covers 8a, 8b, which close the cylinder chambers 3a, 3b, is installed to opposite ends of the main cylinder body 2 respectively.
However, in the case of the linear actuator 1 concerning the conventional technique as described above, it is demanded that the number of parts is reduced in order to reduce the cost of the linear actuator 1 and improve the assembling operability for the linear actuator 1.
Further, the long hole 4 penetrates as far as the lower surface of the main cylinder body 2, while the long hole 4 is open at the lower surface. Therefore, any dust or the like enters the cylinder chambers 3a, 3b via the long hole 4 from the outside of the main cylinder body 2. Further, any dust or the like, which is generated in the cylinder chambers 3a, 3b, is discharged to the outside via the long hole 4.
A finish machining may be applied to the inner circumferential surfaces of the cylinder chambers 3a, 3b in order to reduce the sliding resistance of the outer circumferential surfaces of the sliding pistons 5a, 5b. However, the machining operation to the finish machining is complicated, and the machining cost thereto is expensive.
A first object of the present invention is to provide a linear actuator which can be produced inexpensively by simplifying the structure thereof.
A second object of the present invention is to provide a linear actuator so that it possible to improve the assembling operability for the linear actuator.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.